Joint Toyota-BMW Hybrid Sports Car To Use Supercapacitors From Le Mans Program

BMW has announced more details of the hybrid sports car project it's developing in conjunction with Toyota, confirmed last year.

While the two vehicles will be very different in terms of styling and execution, BMW will rely on hybrid technology developed by Toyota for the vehicle--specifically, technology forged in the crucible of Le Mans endurance racing.

Autocar has revealed both cars will use supercapacitors as energy storage in the hybrid system, a technique directly influenced by Toyota's Le Mans Prototype sports car program.

The benefit of supercapacitors over typical lithium-ion batteries is twofold. The weight penalty of heavy battery packs will be drastically reduced, but high charge and discharge rates are also useful in a vehicle with heavy power requirements.

The weight and power needs of Toyota's Le Mans car are more extreme than those of a sports road car, but similar in nature. Light weight is vital to the car's speed and handling, while heavy acceleration and braking events mean rapid discharging and charging is required to maximize performance.

As with batteries, the supercapacitors would store kinetic energy expended during deceleration or braking as electrical energy, ready to be used for bursts of power at the electric motor.

The new system will differ from the Yaris-R's setup, which put most of its power to the front wheels and electric assistance at the rear, but Toyota told Autocar that the basics will be carried over.

The engine itself will be a BMW design, as will the electric motors, to Toyota specifications. A sequential manual gearbox is planned, and Toyota is working on a torque vectoring ability for the power electronics.

BMW will be responsible for the car's body-engineering too, using lessons learned on the i3 and i8 plug-in vehicles. That means widespread use of carbon fiber reinforced plastic, as well as high-strength steel and aluminum.